relay and related method

ABSTRACT

A relay method comprising receiving data from a first node and a second node; estimating the symbols in the data received from said first node and said second node; transmitting the estimated data from the first node to the second node and the estimated data from the second node to the first node.

FIELD OF THE INVENTION

The present invention relates to a relay and a method of relayingsignals.

BACKGROUND OF THE INVENTION

Network using relays for forwarding information are well known. Inwireless networks such as cellular wireless networks, it is known toprovide relay units for signals for transmitting between a base stationand user equipment such as a mobile terminal or the like. For example,the radio signal transmitted by a base station may be received by therelay and re-transmitted by that relay to the user equipment. Likewise,a signal from user equipment is transmitted and received by the relayand is then re-transmitted by the relay unit to the base transceiverstation.

A relay can be used for a number of different reasons. In one scenario,the use of a relay station means that the effective area of coverage ofa base station can be increased. In other scenarios, the use of a relaystation means that the power with which a base station needs to transmitcan be reduced.

In some scenarios, bidirectional traffic may exist between two nodes(such as a base station and a user equipment) which communicate via arelay node.

In one known scenario, in a first time slot, the first node transmits tothe relay. In a second time slot, the second node transmits to therelay. In a third time slot, the relay transmits the signal from thefirst node to the second node. In the fourth slot, the relay transmitsthe signal from the second node to the first node. This is a basicexample of bidirectional relaying.

More complex forms of bidirectional relaying have been proposed, oneexample of which is the decode-and-forward (DF scheme). The relaydecodes data received from the first node and the second noderespectively. The composite data is encoded with a bitwise XOR(Exclusive OR) operation, amplified and transmitted to the first andsecond nodes at the same time. However, this scheme does have thedisadvantage that it cannot be used with complex symbols in that thescheme operates at the bit level.

Another known scheme is the so-called amplify-and-forward (AF scheme).This is discussed in Petar Popovski, Hiroyuki Yomo, “Bi-directionalAmplification of Throughput in a Wireless Multi-Hop Network”, VehicularTechnology Conference, IEEE 63rd, vol. 2, pp. 588-593, 2006. In thisscenario, the first node requires knowledge of the channel stateinformation (CSI) between the relay and the second node in order todetect the signal from the second node, and vice-versa. However, inorder to obtain the necessary CSI results in a relatively largesignalling overhead.

Reference is made to A Sendonaris, “Advanced Techniques forNext-Generation Wireless Systems”, Ph.D. Thesis, Rice University, August1999. This discusses various aspects of relays.

By way of background only, reference is made to K. Witrisal, Y. H. Kim,R. Prasad, and L. P. Lighthart, “Pre-equalization for the Up-link of TDDOFDM Systems”, Personal, Indoor and Mobile Radio Communications, 12thIEEE International Symposium, vol. 2, pp. 93-98, 2001. This disclosespre-equalization for the uplink of a TDD OFDM (time division duplexorthogonal frequency division multiplexing) system. This is not in thecontext of a relay scenario.

It is an aim of some embodiments of the present invention to address ormitigate one or more of the problems discussed.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided arelay method comprising receiving data from a first node and a secondnode; estimating the symbols in the data received from said first nodeand said second node; transmitting the estimated data from the firstnode to the second node and the estimated data from the second node tothe first node.

According to another aspect of the present invention, there is provideda relay comprising a receiver configured to receive data from a firstnode and a second node; an estimator configured to estimate the symbolsin the data received from said first node and said second node; and atransmitter configured to transmit the combined data from the first nodeto the second node and the estimated data from the second node to thefirst node.

According to further aspect of the present invention, there is provideda relay method comprising pre-equalising a first signal to betransmitted at a first node; transmitting from said first node saidpre-equalised first signal to a relay; pre-equalising a second signal tobe transmitted at a second node; transmitting from said second node saidpre-equalised second signal to said relay; receiving said signalstransmitted by said first and second nodes and said relay; andtransmitting said received signals to said first and second nodes fromsaid relay.

According to another aspect of the present invention, there is provideda relay system comprising a first node, a second node and a relaytherebetween, said first node being configured to pre-equalise a firstsignal and transmit from said first node said pre-equalised first signalto said relay, said second node being configured to pre-equalise asecond signal and to transmit from said second node said pre-equalisedsecond signal to said relay, and said relay being configured to receivesaid signals transmitted by said first and second nodes and to transmitsaid received signals to said first and second nodes.

According to a further aspect of the present invention, there isprovided a node configured to pre-equalise a first signal and transmitsaid pre-equalised signal to a relay, to receive a signal from a relayand to process said received signal to remove a component based on saidfirst signal therefrom to estimate a signal transmitted from a secondnode to said node via said relay.

BRIEF DESCRIPTION OF DRAWINGS

For a better understanding of the present invention and as to how thesame may be carried out, reference will now be made by way of exampleonly to the accompanying drawings in which:

FIG. 1 a illustrates conventional bidirectional relaying;

FIG. 1 b illustrates conventional decode-and-forward bidirectionalamplification of the throughput (DF BAT);

FIG. 1 c shows conventional amplify-and-forward BAT relaying;

FIG. 1 d shows a decode-and-forward scheme embodying the presentinvention;

FIG. 1 e shows an amplify-and-forward scheme embodying the presentinvention;

FIG. 2 shows a flow diagram of a method in accordance with thedetect-and-forward scheme embodying the present invention;

FIG. 3 is a flow diagram of the amplify-and-forward method embodying thepresent invention;

FIG. 4 schematically shows a first relay node embodying the presentinvention;

FIG. 5 schematically shows a second relay node embodying the presentinvention; and

FIG. 6 shows one example of a communication network within whichembodiments of the present invention may be implemented.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Reference will now be made to FIGS. 1 a to e. Whilst FIGS. 1 a to c showconventional bidirectional relaying scenarios, they will be discussed inmore detail in order to facilitate an understanding of the embodimentsof the present invention.

Reference will now be made generally to FIGS. 1 a to e. In FIGS. 1 a to1 e, there is an initial transmitter of signals and also a recipient.Node C is the recipient of the signal transmitted by Node A and also atransmitter of signals to Node A. Nodes A and C communicate via Node Bwhich is a relay node. This notation of Nodes A, B and C is used in eachof the FIGS. 1 a to 1 e. The representations of FIGS. 1 a to e show thesignal flow in four consecutive time slots in the case of FIG. 1 a,three consecutive time slots in relation to FIGS. 1 b and 1 d, and twoconsecutive time slots in relation to FIGS. 1 e and 1 e.

Referring first to FIG. 1 a, this shows that the first node, Node Awants to transmit a packet X_(AC) to Node C. Accordingly, in slot 1, thefirst node, Node A transmits the packet X_(AC) to the relay, that isNode B. h_(AB) represents the channel fading coefficient between thefirst node, Node A, and the relay, Node B. This is the channel impulseresponse.

In the next time slot, time slot 2, the second node, Node C transmits apacket X_(CA) to the relay node, Node B. This packet is intended for thefirst node, Node A. h_(CB) represents the channel fading coefficientbetween the second node, Node C and the relay, Node B. In the third timeslot, the relay node, Node B transmits the packet which it has receivedfrom the first node, Node A to the second node, Node C. The packet whichis transmitted by the relay node is {circumflex over (X)}_(AC). Therelay node, node B thus transmits the estimates of the packet X_(AC)transmitted by the first node. Likewise, in the fourth slot, the relaynode transmits the packet which is the estimates of the packet X_(CA)received from the second node, to the first node.

Reference is now made to FIG. 1 b which shows a decode-and-forwardscheme. In this scenario, the signalling which takes place in the firsttwo time slots is the same as in the arrangement shown in FIG. 1 a.However, in the third time slot the relay node, Node B decodes the datawhich has been received from the first and second nodes respectively.The relay, Node B, applies a canonical network coding operation andbroadcasts the packet x_(B)={circumflex over (x)}_(AC)⊕{circumflex over(x)}_(CA) where ⊕ denotes the bitwise XOR operation. In other words thepackets received by the relay nodes from the first and second nodes arecombined in a bitwise operation. Since the first node Node A already hasknowledge of x_(AC), the first node extracts the required packet{circumflex over (X)}_(CA) through {circumflex over(x)}_(CA)=x_(B)⊕x_(AC). Similarly, the second node, Node C extracts therequire packet {circumflex over (x)}_(AC)=x_(B)⊕x_(CA). The relayingmethod of FIG. 1B requires only 3 time slots to transfer the packetsx_(AC) and x_(CA). However, this method has to be performed at the bitlevel.

Reference is now made to FIG. 1 c which shows an amplify-and-forwardscheme which has previously been proposed. This proposal is able tooperate at the symbol level. In the first time slot, both the firstnode, Node A and the second node, Node C transmit at the same time tothe relay node, Node B. The first node, Node A, transmits the packetX_(AC) whilst the second node, Node C, transmits the packet X_(CA).Assuming that x_(AC) and x_(CA) are the complex baseband at the symbolslevel, and that the expected values are E{x_(AC)}=E{x_(CA)}=0 andE{|x_(AC)|²}=E{|x_(CA)|²}=1, the received symbol y_(B) at the relaynode, Node B can be written as:

y _(B) =h _(AB) x _(AC) +h _(CB) x _(CA) +n _(B)  (2.1)

The value n_(B) is a complex value additive Gaussian white noise at thereceiver of the relay, Node B with variance σ_(B) ². During the secondtime slot, the relay, Node B amplifies y_(B) with a normalization factorβ and broadcasts the resulting signal to both first node and the secondnode. The signal y_(A) received by the first node, Node A can bewritten:

$\begin{matrix}\begin{matrix}{y_{A} = {{\beta \; h_{BA}y_{B}} + n_{A}}} \\{= {{\beta \; h_{BA}h_{AB}x_{A\; C}} + {\beta \; h_{BA}h_{CB}x_{CA}} +}} \\{{{\beta \; h_{BA}n_{B}} + n_{A}}}\end{matrix} & (2.2)\end{matrix}$

n_(A) is a complex value additive Gaussian white noise at the receiverof the first node, Node A.

The average transmitted signal energy over one symbol period at therelay is the same as at the first node such that

$\begin{matrix}{\beta = \sqrt{\frac{1}{{h_{AB}}^{2} + {h_{CB}}^{2} + \sigma_{B}^{2}}}} & (2.3)\end{matrix}$

Assuming the first node, Node A has the CSI knowledge of h_(AB), h_(BA),h_(CB) and β, the transmitted signal by the first node can be subtractedfrom received signal as

$\begin{matrix}\begin{matrix}{r_{A} = {{\beta \; h_{BA}h_{AB}x_{A\; C}} + {\beta \; h_{BA}h_{CB}x_{CA}} +}} \\{{{\beta \; h_{BA}n_{B}} + n_{A} - {\beta \; h_{BA}h_{AB}x_{A\; C}}}} \\{= {{\beta \; h_{BA}h_{CB}x_{CA}} + {\beta \; h_{BA}n_{B}} + n_{A}}}\end{matrix} & (2.4)\end{matrix}$

Then x_(CA) can be estimated as

{circumflex over (x)} _(CA)=β⁻¹ h _(BA) ⁻¹ h _(CB) ⁻¹ r _(A)  (2.5)

βh_(ba)n_(B)+n_(A) is included in r_(A), and the term is the noise thatcan not be cancelled, thus this gives the estimated data with error dueto this term

Similarly, x_(AC) can be estimated as

r _(C) =βh _(BC) h _(AB) x _(AC) +βh _(BC) n _(B) +n _(C)  (2.6)

{circumflex over (x)}_(AC)=β⁻¹h_(BC) ⁻¹h_(AB) ⁻¹r_(C)  (2.7)

n_(c) is a complex value additive Gaussian white noise at the receiverof the second node, Node B.

It can be noticed that the requirements for knowledge of the CSI betweenthe relay and source nodes, and CSI between the relay and destinationnodes may require a large signalling overhead.

Reference is now made to FIG. 1 d which shows a detect-and-forwardscheme embodying the present invention.

As shown in FIG. 1 d, during the first time slot, the received symbol atthe relay from the first node is:

y _(B1) =h _(AB) x _(AC) +n _(B)  (3.1)

The received signal is then equalized in the relay and the transmittedsignal from the first node, node A can be estimated by hard-decisions atthe symbol level as

$\begin{matrix}\begin{matrix}{{\hat{x}}_{A\; C} = {h_{AB}^{- 1}y_{B\; 1}}} \\{= {h_{AB}^{- 1}\left( {{h_{AB}x_{A\; C}} + n_{B}} \right)}} \\{= {x_{A\; C} + {h_{AB}^{- 1}n_{B}}}}\end{matrix} & (3.2)\end{matrix}$

Similarly during the second time slot, the received signal y_(B2) fromthe second node, Node C, is equalized. This is channel equalisation. Thetransmitted signal from node C can be estimated by hard-decisions at thesymbol level as

$\begin{matrix}\begin{matrix}{{\hat{x}}_{CA} = {h_{CB}^{- 1}y_{B\; 2}}} \\{= {h_{CB}^{- 1}\left( {{h_{CB}x_{CA}} + n_{B}} \right)}} \\{= {x_{CA} + {h_{CB}^{- 1}n_{B}}}}\end{matrix} & (3.3)\end{matrix}$

The hard-decision symbols from both the first and second nodes aresummed as

y _(B) ={circumflex over (x)} _(AC) ÷{circumflex over (x)} _(CA)  (3.4)

During the third time slot, the relay amplifies y_(B) with anormalization factor β and broadcasts it to both the first node A andsecond node C. The received signal at the first node A can be writtenas:

$\begin{matrix}\begin{matrix}{y_{A} = {{\beta \; h_{BA}y_{B}} + n_{A}}} \\{= {{\beta \; {h_{BA}\left( {{\hat{x}}_{A\; C} + {\hat{x}}_{CA}} \right)}} + n_{A}}}\end{matrix} & (3.5)\end{matrix}$

where

$\begin{matrix}\begin{matrix}{\beta = \sqrt{\frac{1}{{E\left\{ {{\hat{x}}_{A\; C}}^{2} \right\}} + {E\left\{ {{\hat{x}}_{CA}}^{2} \right\}}}}} \\{= \sqrt{\frac{1}{2}}}\end{matrix} & (3.6)\end{matrix}$

With the knowledge of h_(BA), x_(AC) and β, x_(CA) can be estimated as:

{tilde over (x)}_(CA)=β⁻¹h_(BA) ⁻¹r_(A)  (3.7)

where

$\begin{matrix}\begin{matrix}{r_{A} = {y_{A} - {\beta \; h_{BA}x_{A\; C}}}} \\{= {{\beta \; h_{BA}{\hat{x}}_{A\; C}} + {\beta \; h_{BA}{\hat{x}}_{CA}} + n_{A} - {\beta \; h_{BA}x_{A\; C}}}} \\{= {{\beta \; h_{BA}{\hat{x}}_{CA}} + n_{A} + {\beta \; {h_{BA}\left( {{\hat{x}}_{A\; C} - x_{A\; C}} \right)}}}}\end{matrix} & (3.8)\end{matrix}$

Likewise, x_(AC) can be estimated as

{tilde over (x)}_(AC)=β⁻¹h_(BC) ⁻¹r_(C)  (3.9)

where

r _(C) =βh _(BC) {circumflex over (x)} _(AC) +n _(C) +βh_(BC)({circumflex over (x)} _(CA) −x _(CA))  (3.10)

Reference is now made to FIG. 2 which illustrates a flow diagram of themethod described, in relation to FIG. 1 d. Firstly, as indicated byreference S1, a packet is transmitted from the first node to the relay.

As indicated by S2, at the relay, the received packet from the firstnode is equalised and a hard decision is made at the symbol level.

In the next stage, S3, a packet is transmitted from the second node tothe relay.

As a fourth stage, S4, the relay equalises and makes a hard decision atthe symbol level in respect of the packet received from the second node.It should be appreciated that stages S2 and S4 may take place more orless at the same time. Stage S2 can be carried out after stage S3 orbefore.

In stage S5, the relay sums the hard decision symbols in respect of thepacket received from the first node and the second node, amplifies theresult and transmits the resulting symbols to both the first node andthe second node.

Stages S6 and S7 may take place more or less at the same time or oneafter the other. Stage S6 comprises the second node estimating thepacket transmitted from the first node whilst stage S7 comprises thefirst node estimating the packet transmitted from the second node.

Reference is now made to FIG. 1 e which shows a second embodiment of theinvention. This embodiment is an amplify-and-forward embodiment whichuses pre-equalisation to avoid the need for signalling overhead as shownin the example of FIG. 1 c. During the first time slot, the first nodeand the second node transmit h_(AB) ⁻¹x_(AC) and h_(CB) ⁻¹x_(CA)respectively to relay node B simultaneously or at more or less the sametime with pre-equalization. In other words, the first node and secondnode apply pre-equalisation to the packet before the packet istransmitted. The pre-equalisation is to compensate for the effects ofthe channel. The received data at the relay can be written as

$\begin{matrix}\begin{matrix}{y_{B} = {{h_{AB}h_{AB}^{- 1}x_{A\; C}} + {h_{CB}h_{CB}^{- 1}x_{CA}} + n_{B}}} \\{= {x_{A\; C} + x_{CA} + n_{B}}}\end{matrix} & (3.11)\end{matrix}$

During the second time slot, the relay amplifies y_(B) with anormalizing factor β and broadcasts it to both the first node and thesecond node, where the average transmitted signal energy over one symbolperiod at the relay is the same as the first node as

$\begin{matrix}\begin{matrix}{\beta = \sqrt{\frac{1}{{E\left\{ {x_{A\; C}}^{2} \right\}} + {E\left\{ {x_{CA}}^{2} \right\}} + \sigma_{B}^{2}}}} \\{= \sqrt{\frac{1}{2 + \sigma_{B}^{2}}}}\end{matrix} & (3.12)\end{matrix}$

The received signal at the first node is

$\begin{matrix}\begin{matrix}{y_{A} = {{\beta \; h_{BA}y_{B}} + n_{A}}} \\{= {{\beta \; h_{BA}x_{A\; C}} + {\beta \; h_{BA}x_{CA}} + {\beta \; h_{BA}n_{B}} + n_{A}}}\end{matrix} & (3.13)\end{matrix}$

With the knowledge of h_(BA), x_(AC) and β, x_(CA) can be estimated as

{circumflex over (x)}_(CA)=β⁻¹h_(BA) ⁻¹r_(A)  (3.14)

where

$\begin{matrix}\begin{matrix}{r_{A} = {{\beta \; h_{BA}x_{A\; C}} + {\beta \; h_{BA}x_{CA}} + {\beta \; h_{BA}n_{B}} + n_{A} - {\beta \; h_{BA}x_{A\; C}}}} \\{= {{\beta \; h_{BA}x_{CA}} + {\beta \; h_{BA}n_{B}} + n_{A}}}\end{matrix} & (3.15)\end{matrix}$

Likewise, x_(AC) can be estimated as

{circumflex over (x)}_(AC)=β⁻¹h_(BC) ⁻¹r_(C)  (3.16)

where

r _(C) =βh _(BC) x _(A) +βh _(BC) n _(B) +n _(C)  (3.17)

Thus, in this embodiment, it is possible to estimate the signals from asource node at a destination node without requiring information as tothe CSI between the source node and the relay node.

Reference is made to FIG. 3 which shows a flow diagram illustrating themethod of the second embodiment of the invention.

In stage T1, a packet is pre-equalised in the first node and transmittedby the first node to the relay. In the second stage T2, a packet apre-equalised in the second node and is transmitted by the second nodeto the relay. It should be noted that stages T1 and T2 may take place atthe same time, or one stage may take place before or after the other.

In stage T3, the relay amplifies the received signal from the first andsecond nodes and broadcasts the combined signal to the first and secondnodes. In one alternative embodiment, the relay may transmit to thefirst and second nodes at different respective times.

In stage T4, the second node estimates the packet transmitted by thefirst node from the broadcast received from the relay. Likewise, instage T5, the first node estimates the packet transmitted by the secondnode and received from the relay. It should be appreciated that stagesT4 and T5 can take place more or less at the same time or one after theother.

FIG. 4 shows a first relay embodying the present invention, and inparticular, a relay suitable for implementing the embodiment describedin relation to FIG. 1 d. The relay 20 comprises an antenna 22. Theantenna 22 is connected to transmitting circuitry 10 and receivingcircuitry 12. Signals which are received by the antenna 22 are passed tothe receiving circuitry 12. This receiving circuitry will convert thereceived signals to a baseband signal which is passed to an equaliser14. The equaliser equalises the received signal and provides an outputto the estimator 15 which makes hard decisions at the symbol level. Theestimated symbols 15 are output to a summer 16. The summer 16 isarranged to sum the estimated symbols received from the first node withthe estimated symbols received the second node. The summed symbols areoutput to the amplifier 18 which amplifies the symbols. The amplifiedsymbols are output to the transmitting circuitry 10 which converts thesignals which are at the baseband to the required radio frequency andpasses the radio frequency signals to the antenna 22 for transmission.

FIG. 5 shows a second relay embodying the present invention and inparticular a relay suitable for implementing the embodiment described inrelation to FIG. 1 e. The relay comprises an antenna 32 connected totransmitting circuitry 34 and receiving circuitry 35. The relay receivessignals from the first and second nodes via the receiving circuitry 35which converts the received signals to the base band. A summer 39 sumsthe base band signals received from the two nodes and passes the summedsignal to an amplifier 37 which amplifies the combined signal. Thecombined signal is then passed to the transmitting circuitry 34 whichconverts the signal to the radio frequency for transmission by theantenna 32.

It should be appreciated that in alternative embodiments of theinvention, the relay node does not need to reduce the signal to thebaseband but instead processes the signal at the radio frequency level.

One example of a network within which embodiments of the presentinvention may be incorporated will now be described with reference toFIG. 6.

A communication device, for example a user device can be used foraccessing various services and/or applications provided by acommunications system. In the context of the examples previously given,the communication device would be one of the first and second nodes. Inwireless or mobile systems, the access is provided via an accessinterface between a user device and an appropriate wireless accesssystem. The user device can typically access wireless communicationssystem via at least one base station or similar wireless transmitterand/or receiving node via a wireless connection 11. In the context ofembodiments of the invention, the wireless communication 11 will be withrelay 44, embodying the present invention. A further wireless connectionwill be provided between the relay 44 and the base station 45. Withreference to FIG. 1, the relay 44 corresponds to Node B. One of the basestation and user equipment will be the first node whilst the other ofthe user equipment and the base station will be the second node.

Examples of access nodes include a base station of a cellular system anda base station of a wireless local area network.

The base station may be connected to other systems, for example a datanetwork 42. A gateway function between a base node and other network maybe provided by means of any appropriate gateway node 44, for example apacket data gateway and/or an access gateway.

A base station is typically controlled by at least one appropriatecontroller entity 46. The controller entity can be provided for managingthe overall operation of the base station and communications via thebase station. The controller entity is typically provided with memorycapacity and at least one data processor. Functional entities may beprovided in the controller by means of data processing capabilitiesthereof. The functional entity provided in the base station controllermay provide function relating to radio resource control, access control,packet data context control and so forth.

Certain embodiments of the present invention can be used in the longterm evolution (LTE) radio system. This system provides an evolved radioaccess system that is connected to a packet data system. Such an accesssystem may be provided, for example, based on architecture that is knownfrom the E-UTRA (evolved UMTS(Universal mobile telecommunicationssystem) terrestrial radio access) and based on the use of E-UTRAN nodeBs (ENBs).

It should be appreciated that the architecture shown in FIG. 6 is by wayof example only and there are other networks with which embodiments ofthe present invention may be used.

Some embodiments of the present invention may be used with the proposedIMT IMT (International Mobile Telecommunications)-Advanced system.

Alternatively, embodiments of the present invention may be used with thewireless local area network type arrangement.

The user device 1 can be used for various tasks such as making andreceiving telephone calls, the receiving and sending data from and to adata network and for experiencing, for example, multimedia or othercontent. For example, a user device may access data application providedby a data network.

An appropriate user device may be provided by any device capable ofsending and receiving radio signals. Non-limiting examples include amobile station (MS), a portable computer provided with a wirelessinterface card or other wireless interface facility, a personal dataassistant (PDA) provided with wireless communication capabilities, orany combination of these or the like.

The mobile device may communicate via an appropriate radio interfacearrangement of the mobile device. The interface arrangement may beprovided for example by means of a radio part 7 and an associatedantenna arrangement.

The mobile device is typically provided with at least one dataprocessing entity 3 and at least one memory 4 for use in tasks such asit is designed to perform. The data processing and storage entities canbe provided on an appropriate circuit board, on an integrated circuit orin chipsets. This is denoted by reference 6.

Also shown is a modulated component 9 connected to the other elements.It should be noted that the modulated function may be arranged to beprovided by the data processing entity 3 instead of via a separatecomponent.

The user can control operation of the mobile device by means of asuitable user interface such as a keypad 2, voice commands,touch-sensitive screen or pad, combination thereof or the like. Adisplay 5, a speaker and a microphone are also typically provided.Furthermore, a mobile device may comprise appropriate connectors (eitherwired or wireless) to either devices and/or for connecting externalaccessories, for example hands-free equipment thereto.

It should be appreciated that in the context of the first embodiment theprocessor 3 of the user device will carry out the calculation toestimate X_(AC) or X_(CA), depending on which of the nodes the userequipment is regarding as being.

The memory 4 will be arranged to store the values of H_(BA), X_(AC) andβ in the case that X_(CA) is being calculated or H_(BC), X_(AC) and B inthe case that X_(AC) is being calculated. It should be appreciated thatin some embodiments of the present invention, knowledge of the channelcharacteristic will be calculated by the user device.

It should be appreciated that the base station will similarly have dataprocessing capacity 50 and memory 52 such that it can also make anestimation as to the packet which is being transmitted to it from theuser equipment.

In order to perform the second embodiment, the user equipment and alsothe base station will be provided a pre-equaliser 56 and 58 respectivelywhich will pre-equalise the packet before transmitting it to the relay.

It should be appreciated that embodiments of the present invention canbe used in any context where a first node and a second node communicatevia a relay.

It should be noted that although certain embodiments are being describedby way of example with reference to certain exemplifying architectures,embodiments may be apply to any other suitable form of communicationssystem and may at least be partially implemented by a computer program.For example, any one or more of the equations which are required to beperformed may be carried by a computer program by means of a suitableprocessor or the like. It is also noted here whilst the above-describedexemplifying embodiments of the invention have been described, there areseveral variations and modifications which may be made without theparting from the scope of the present invention.

1. A relay method comprising: receiving data from a first node and asecond node; estimating symbols in the data received from said firstnode and said second node; transmitting the estimated data from thefirst node to the second node and the estimated data from the secondnode to the first node.
 2. A relay method as claimed in claim 1,comprising receiving the data from the first node and the second node atsubstantially the same time. 3-29. (canceled)
 30. A relay method asclaimed in claim 1, comprising summing the estimated symbols for thedata from the first node and the estimated symbols for the data from thesecond node.
 31. A relay method as claimed in claim 30, whereintransmitting the estimated data to said first and second nodes comprisestransmitting the summed estimated symbols.
 32. A relay method as claimedin claim 31, comprising transmitting the estimated data to the first andsecond nodes at the same time.
 33. A relay method as claimed in claim32, comprising equalising said data from the first node and from thesecond node.
 34. A relay method as claimed in claim 33, comprisingamplifying said estimated data prior to transmitting said estimateddata.
 35. A relay comprising; a receiver configured to receive data froma first node and a second node; an estimator configured to estimatesymbols in the data received from said first node and said second node;and a transmitter configured to transmit combined data from the firstnode to the second node and the estimated data from the second node tothe first node.
 36. A relay as claimed in claim 35, comprising a summerconfigured to sum the estimated symbols for the data from the first nodeand the estimated symbols for the data from the second node.
 37. A relayas claimed in claim 35, comprising an equaliser configured to equalisesaid data from the first node and from the second node.
 38. A relay asclaimed in claim 35, comprising an amplifier for amplifying saidestimated data prior to transmitting said estimated data.
 39. A relaymethod comprising: pre-equalising a first signal to be transmitted at afirst node; transmitting from said first node said pre-equalised firstsignal to a relay; pre-equalising a second signal to be transmitted at asecond node; transmitting from said second node said pre-equalisedsecond signal to said relay; receiving said signals transmitted by saidfirst and second nodes and said relay; and transmitting said receivedsignals to said first and second nodes from said relay.
 40. A relaymethod as claimed in claim 39, comprising combining said signalstransmitted by said first and second nodes at said relay
 41. A relaymethod as claimed in claim 39, comprising transmitting said firstpre-equalised and said second pre-equalised signals at substantially thesame time.
 42. A relay method as claimed in claim 39, comprisingtransmitting said received signals to said second and first nodes atsubstantially the same time.
 43. A relay method as claimed in claim 39,comprising receiving said first and second signals at said relay,wherein said pre-equalising compensating for channel effects betweensaid first node and said relay, and between said second node and saidrelay respectively.
 44. A relay method as claimed in claim 39,comprising amplifying at the relay, the received signals prior totransmitting by said relay.
 45. A relay method as claimed in claim 39,comprising receiving at one or both of said first and second nodes saidsignals transmitted by said relay.
 46. A relay method as claimed inclaim 45, comprising processing at said first node said signals receivedfrom said relay to remove a component based on said first signaltherefrom to estimate a signal transmitted from said second node to saidfirst node via said relay.
 47. A relay method as claimed in claim 45,comprising processing at said second node said signals received fromsaid relay to remove a component based on said second signal therefromto estimate a signal transmitted from said first node to said secondnode via said relay.